Fingerprint identification systems usually include capacitive or optical surface-area sensors for identifying characteristic features of a fingertip. The detected signals are often compared by a detecting device with fingerprint features of authorized persons, with these features being stored in a memory. If the fingerprint detected by the fingerprint sensor matches a stored fingerprint pattern in terms of essential features, the detecting device outputs a corresponding signal to an evaluation and control device, which unlocks, for example, a door lock. If an unauthorized person, for example, attempts to gain access, this is identified by a comparison of the detected fingerprint features of the unauthorized person with the stored fingerprint features and signal transmission to the evaluation and control device is either blocked or a failed-attempt signal is transmitted. The reliable identification of deceptive attempts, for example, a severed finger of an authorized person or a film or the like with the fingerprint of an authorized person, has proven to be problematic.
DE 20 2004 001 624 U1 discloses a fingerprint verification device with at least one fingerprint detecting device connected to an evaluation and control device. The fingerprint detecting device has a line sensor and evaluation electronics and the evaluation and control device is connected to an access-control device, in particular, with a break-in alarm system. In order to increase security standards, line sensors are provided that are less easy to sabotage than surface-area sensors, since an image of the entire fingertip is generated successively by slowly moving the finger over the line sensor. In addition, the line sensor has several resistive, temperature-dependent elements, in order to prevent incorrect identification through the use of a film with a fingerprint of an authorized person or a severed finger of an authorized person.
In addition, DE 699 20 126 T2 shows a fingerprint reading device with a light source, a photosensor device, which includes several photosensors constructed on the light source and also a surface constructed on the photosensors, and a transparent layer that is transparent to light and that is constructed on the photosensor device. In order to recognize the use of a fingerprint copied onto a sheet of paper, the electrical resistance of a finger, which is not present when a sheet is used, is detected in the fingerprint reading device when the two-dimensional photosensor having a pair of transparent conductive layers is contacted by a finger.